Have him add fiber to his diet. Either metamucil powder (follow directions but only use 1/2 cup water) or metamucil cookie/wafers. That product will help to absorb excess water until his new plumbing adapts. Eliminate anything with sugar in it, including fruit juices. Sugar makes things loose. Also eliminate carbonated beverages until he is beyond the adaption phase. Eat more bulking foods like rice, pasta, oatmeal, and bananas. I recommend canned vegetables until he's a bit further along. He can really up the imodium. Remember, his intake of fiber and imodium will be trial and error until he finds the right balance.